Reaction of substituted sulfenamides with ketones and use of reaction product in rubber vulcanization



Patented Jan. 8, 1952 REACTION OF sUBsTITU'rEn 'SULFENA- MIDES WITH KETONES AND USE OF RE- ACTION PRODUCT IN RUBBER VULCANI- Edward, L. Carr, Akron, Ohio, assignor to The Eirestoneilire. & Rubber Company, Akron, Ohio, a corporatiqn of Ohio N-orDrawing. Application July 2, 1949, .Sfiiiial No. 102,937

23 Claims. 1

Th s "inventionzrelates' to reaction products. o ket nesand suif namides andtothe metho o :pr ducingthe. same. The 'suifenamides co te plated areithe.thiazole thiazoline and thiocarbamyl S1117 fenam'ides having at leas one hydr en a om irectlyi-attachedtothe amide nitmeenatom- This classsofcsubstit ltfid .sulfenamides has heretofore foundintility: as ;rubbervulcanization. a celerators andralsolas. iungicideabut many-members Of th classare liquidsor melt at low temperatures and decom osemstoraee-under ordinarvatmcspheric conditions.

It is an object or the n enti n o produ e hi her meltmgsand more, stab e composition from the above class of substituted .Sulfenamides. Other' objects will be apparent in the descriptionoithe invention-whichfollows.

' The objects of the invention are realized by reacting a substituted sulfenamide-of the above class withaketone. "Ihe reaction may be carried out by intimately mixing the sulfenamide with the ketone and allowing the mixture to stand at ordinary ,or room temperature. When liquid ketonesare employed, no other solvent is ordinarily necessary, since-it is usually desirable to use an excess of the leetone, in order completely to dissolve the sulfenamide. In some cases, however, an inert solvent, such as benzene, gasoline or the like, may be added :to insure complete mixing of the two reactants. High reaction temperatures are ordinarily to be avoided, since decomposition and/ or resiniiieationpiten occurs at temperatures in the order of 100 C. or higher.

7 Theexaet nature of the -reaction and products of the invention is not completely=-understood Although it is -'believed -that-one-or more condensation reactions-may "beinvolved, the-apparently complex structures-of thereaction prodnets of the invention has made it diflicult to assign chemical structures to them'with confidence.

The ---sulfenamides suitable for use in the-reaction f the invention are represented "by" the iollowing'formulast I. Thiazolesulrenamides:

.IL flhiazo nesulfenamid sz III. Thiocarbamyl sulienamides:

wherein R. and R, which may all be-the same or different, are hydrogen, a hydrocarbon alkyl (includin -z h d o a b n cvc oa kyb hydroca bon aryl. hydrocarbon a alk l. iurf ry Qr te ra hydroiur u v r d eals; B" i a hydrocarbon a ivl. (includin h d ocarbon cyc oa sylb hydro car on and. h d ca bon a al yl. ur uryl or tetrahydrofurfuryl radical. Furthermore, in Formula I the two 13, groupsmay join with the dou e-bonded ca bo vior n y en ad al. ,sucha benzp nan t a' e a y m zo nd the. like. and. Form alll he a R'ma Join ith the ad cent nitwg tofo a h ycli r d cal n which 3'3 1 l yl ne al sylen wxya iy ene. su h as i eri yt m pholyl and similar heterocyclic radicals.

Typical examples of suitable substituted sulfenamides are the following:

N:methyhdsmethylthiazqle sulfenamide N-oyclohexyl.-4=methy1thiazole sulfenamide Nt-cyclohexyl-.4=ethylthiazole suifenamide Ni-eyclohexyls4,5=dimethylthiazole sulfienamide N-isopro.pylesmethylthiazole sulfenamide 4-methylthiazole sulfenamide Thiazole sulfenamide Benzothiazolersulfenamide N-cyclohexyl benzothiazole sulfenamide N-isopropyl benzothiazole sulfenamide Dimethylthiocarbamyl sulfenamide Cyclopentamethylenethiocarbamyl sulfenamide N-cyclohexyl cyclopentamethylenethiacarbamyl sulfenamide N-cyclohexyl dimethylthiocarbamyl sulfenamide Thiazoline sulfenamide N-cyclohexyl thiazoline sulfenamide N-isopropyl thiazolinesulfenamide N-ethyl thiazoline sulfenamide N cyclohexyl 4,4 dimeth-ylthiazoline sulfenam d N-furfuryl thiazoline sulfenamide N-tetrahydrofurfuryl thiazole sulfenamide N-cyclohexyl naphthothiazole sulfenamide N tetrahydrofurfuryl difurf urylthiacarbamyl sulfenamide N- cyclohexyl tet ahydrohenzqth azsole salienamide N-isopropyl tetrahydrobenzothiazole sulfenamide Tetrahydrobenzothiazole sul-fenamide In addition to the sulfenamide vulcanization accelerators mentioned above, other known sul fenamide accelerators having a hydrogen atom directly attached to the amido nitrogen atom may be utilized in the invention, for example, as disclosed in the following United States patents: 2,271,834, 2,339,552, 2,367,827, 2,381,384, 2,381,392 and 2,445,722.

Examples of some suitable ketones are the following:

Acetone Methyl ethyl ketone Methyl propyl ketone Methyl butyl ketone Methyl isopropyl ketone Di-isopropyl ketone Acetonyl acetone Mesityl oxide Phorone Isophorone Methyl vinyl ketone Benzal acetone Acetophenone Benzophenone Acetonaphthone Cyclohexanone Cyclopentanone The following examples are given to illustrate the invention, although it is to be understood that homologs and other reactants, such as those listed .above, may be substituted for the specific reactants of the examples in practicing the invention.

EXAMPLE 1 N-cyclohexyl benzothiazole sulfenamide was dissolved in acetone. In the course of 20 minutes? standing at room temperature, crystals precipitated with a slight heat of reaction. The melting point of the crystals was 185 C., in comparison with a melting point of 102 C. for the reactant sulfenamide.

EXAMPLE 2 A quantity of N-isopropyl benzothiazole sulfenamide (melting point 93 C.) was dissolved in acetone. After standing a few minutes at room temperature, a crystalline product separated. This product had a melting point of 139 C.

The product of Example 1 was tested as a rubber vulcanization accelerator in the following testing formula:

Ingredients Parts by weight Rubber 100 ulfur 3 Stearic acid. 1. 10 Zinc oxide- 5 Accelerator 0.

The test results are recorded in the Table I.

Table I V 600% Modulus in Tensile Strength in lbs/in. lb/in.

Cure in minutes 24 30 60 30 60 90 120 Product of Example 1 75 25 25 50 75 25 v 25 100 I 600% Modulus in Tensile Strength in lbs/in. lbs/in.

Cure in minutes r 20 40 60 100 20 40 60 100 Product of Example 1 75 4 0 700 900 175 1, 950 2, 350 r 2, 000

Thus it is seen that the product of Example 1 is an effective delayed-action accelerator, since it produced substantially no vulcanization of the rubber at the low vulcanizing temperature of 240 F., indicating that rubber compositions utilizing the products of the invention as accelerators are unusually free of any tendency to set-up or pre-cure during processing in the rubber factory, since temperatures as high as 240 F. often are reached in the banbury and during some tubing operations. On the other hand, the high physical properties produced by curing at the usual vulcanizing temperature of 280 F. show that the products of the invention are excellent accelerators.

EXAMPLE 3 Found: C, 59.6%; H, 5.5%; N, 8.4% S, 27.1%. Calculated for C23H25N3S4: C, 58.4%; H, 5.3%; N, 8.9%; S, 27.2%.

Thus the product apparently resulted from condensation of 2 moles of the sulfenamide-with 1 mole of acetone, with the elimination of 1 mole of water and 1 mole of cyclohexylamine. The following structure is proposed for this reaction product:

EXAMPLE 4 The reaction of Example 2 was repeated-under carefully controlled conditions to produce a sample of product for analysis. Twenty-two grams (0.1 mole) of purified N-isopropyl benzothiazole sulfenamide (M. P. 97- 99 C.) was dissolvedin ml. of purified-acetone contained in a glass stoppered flask. The solution was stored in the dark under nitrogen at room temperature. After 5 days the excess acetone was removed under reduced pressure, the flask being heated in a water bath, the temperature of which did not exceed 75 C. :'A very-viscous reddishbrown residue remained. The residue was dissolved in toluene, from which recrystallization of the reaction product was effected by addition of petroleum ether at ice temperatures. After 3 recrystallizations, a. ,white cry stalline solid melting at 132-134 C. was'obtained. Orr-analysis, this product was found to contain 58.1% of carbon and 4.8% of hydrogen.

EXAMPLE 5 Fifteen grams,,(0.06 mole) of recrystallized N-cyclohexyl diethylthiocarbamyl sulfenamide (M. P. 67-68 C.) was reacted with acetone in aware-es 5. accordance with the procedure of *E'xample 4. After days at 'room temperature a dark so1ution resulted. The residue remainingafter-removalof excess acetone was dissolved in toluene and the'crystalline product thrown out by addition of petroleum ether. The product was then recrystallized from toluene. Yield 7 gramswf white crystals melting at 119-120 C. Analysis showed'the'productto contain 56.52% of carbon.

and 10.3% ofhydrogen.

EXAMPLE .6

Ten grams of -N-isopropyl"benzothiazole'siilfenamide (M. P.'97-'99C.') was dissolvedin sufficient methyl ethyl ketone'to insure solution,gand thesolution was allowed to stand at room temperature .for 10 days. After 'remova'liof'yolatile material'from the reaction mixture, as in previous examples, .the residue was crystallized from toluene-petroleum ether as 2.5 'grams'meltingiat.

98-l05 C. The product was recrystallizedirom n'-heptane to yield a pure white crystalline substance melting at 108-110 C. and analyzing 59.6% of carbon and 6.76% of hydrogen.

EXAMPLE 7 Ten grams of N-isopropyl benzothiazole sulfenamide (M. P. 97-99 C.) was dissolved in..38.5 grams of pentanone-2. After themixture vhad stood atv room temperature for '10 days, the volatile material was removed.therefrom-.bydistillation under reduced pressure. The residue was crystallized from n-heptane toyield 4.1 grams of auwhite crystalline solid melting at:125-128 C. and analyzing 59.7% of carbon and 7.2%,.of .hydrogen.

EXAMPLE 8 Ten grams of :N-dsopropyl benzothiazole :sulfenamide was dissolved 57 grams-of methyl hexyl ketone, and the. mixture was vallowedfto stand at room temperaturetforZ weeks. Volatile material was then removed .fromzthe reaction mixture 'under 'a .9 mm; vacuum. .The voilyvresidue was treated with petroleum .cther,:cooled and stirred to crystallize. The crystals were separated and recrystallized from toluene-petroleumether to yield a white crystalline substance melting-at 117-l19 C. and analyzing 51.4% of carbon and 5.4% of hydrogen.

EXAMPLE 9.

Ten grams of N-isopropylbenzothiazolesulfenamide was dissolved. in: 54 grams of ,acetophenone, and the mixture was allowed to stand at room temperature for 3 weeks. Volatilematrial was then removed from the reaction mixture imdera vacuum of 1 .5 mm. The oily residuewas precipitated as a solid by treatment with petroleum ether, and the solid product was then recrystallized from toluene to yield 6.5 grams of a white,crystallinesubstance melting at 177-179? 0. Since this melting point is similar to the melting point of 2,2-dithiobis-benzothiazole (often obtained as a byproduct from reactions involving substituted benzothiazole sulfenamides) a mixed melting point of the reaction product with purified 2,2'-dithiobis-sulfenamide (M. P. 181-182 C.) was determined, and found to be 160-l70 0., thus proving that the reaction product was not this unwanted, possible byproduct. The reaction product was shown on analysis to contain 59.8% of carbon and 3.7% of hydrogen.

ture of ether and n-heptane. However,..this.-..oil

was definitely (largely thev desired .reaction .product, since it wasiobservedto possessrsubstantially difierent .physical rand chemical properties dramthose of the reactants; It was a-nticipatedpthat a .mtystalline product -.-would .be obtained .upon purificationofthe *oilyzproduct by moleculardis: till'ation; .but the necessary apparatus .for this methodiof ,purification-was-not available. Although :no :catalystswere-zemployed .infithe ir-eactions set out in thezcexampl-es, the use-lof appro-' priate :.1catalysts is contemplated --by the invention. isincerit :islikely :that certain condensation reactions are involved .intthe reaetion-.-effthe'in=- VLGIIfiOILil? will :be apparent to those eskilledrinzthe arttomise; certainccondensation catalysts to-spee unitherreaction'. 7

From the above detailed c-description ,Qfwlthfi invention it is apparent that the objects are accomplished by the discovery that substituted sulfenamide accelerators may }?be converted into higher melting and more stable new compounds, which are also delayed-action :yulcanization saccelerators by reaction with a ketone- What is claimed is:

l. A reactionsproduct. ofzasketone: and-ia sulfenq amide having at least .one hydrogen .atom at tachedtto the zamidogznitrogen atom -.thereof and selected fromzthe :group zconsistingqof thiazoline, thiazoleeandl-thiocarbamyl sulf enamides. l

, 1' 2? .A reaction product. of a-sketone and-ta thiazole sulfen'amide ofiithe formula \CS.NR R -s wherein R and R are selected from the group of radicals consisting of hydrogen, hydrocarbon alkyl, hydrocarbon aryl, hydrocarbon aralkyl, furfuryl and tetrahydrofurfuryl and also wherein the two R groups form 1 with thesdoub-le-ibonded carbon atoms .a radical from the grouprconsisting of arylene and partially hydrogenated: arylene.

3. A reaction product'pf allketonesandmxthia zoline sulienamideof'the formula wherein ,ZR and R are selected from the group of ;-radica1s consisting .of hydrogen, hydrocarbon allgyl, .-.hydroca-rbon and, hydrocarbon .aralkyl, furfuryl and tetrahydrofurfuryl.

4. A reaction product of a ketone and a thiocarbamyl sulfenamide of the formula R'-N(J-Sl?I-R wherein R and R are selected from the group of radicals consisting of hydrogen, hydrocarbon alkyl, hydrocarbon aryl, hydrocarbon aralkyl, furfuryl and tetrahydrofurfuryl, R" is selected from the group of radicals consisting of hydrocarbon alkyl, hydrocarbon aryl, hydrocarbon aralkyl, furfuryl and tetrahydrofurfuryl, and also wherein NR'R is a heterocyclic radical in which R'R" is selected from the group of radicals consisting of alkylene and alkylene-oxy-alkylene.

5. A reaction product of a methyl ketone and a sulfenamide vulcanization accelerator having at least one hydrogen atom attached "to the amido nitrogen atom thereof.

v 6. A reaction product of acetone andN-CY O hexvl' benzothiazole sulfenamide.

7. A reaction product of acetone and N-isopropyl benzothiazole sulfenamide.

8. A'reaction product of acetone and N-cyclohexyl' diethylthiocarbamyl sulfenamide 9; The method of making a relatively high melting, stable compos'iti'on'of matter which comprises reacting a ketonewith a sulfenamide having at least one hydrogen atom attached to the amido nitrogen atom thereof and selected from the group consisting of thiazoline, thiazole and thiocarbamyl sulfenamides. 1 10. The method of making a relatively high melting, stable composition of matter which comprises reacting a ketone with a thiazole sulfenamide of the formula wherein R and R are selected from the group of radical consisting of hydrogen, hydrocarbon alkyl, hydrocarbon aryl, hydrocarbon aralkyl, furfuryl and tetrahydrofurfuryl and also wherein the two R groups form with the double-bonded carbon atoms a radical from the group consisting of arylene and partially hydrogenated arylene.

11. The method of making a relatively high melting, stable composition of matter which comprises reacting a ketone with a thiazoline sulfenamide of the formula wherein R and R are selected from the group of radicals consisting of hydrogen, hydrocarbon alkyl, hydrocarbon aryl, hydrocarbon aral y furfuryl and tetrahydrofurfuryl. I

12. The method of making a relatively high melting stable composition of matter which comprises reacting a ketone with a thiocarbamyl sulfenamide of the formula wherein R and R are selected from the'group of radicals consisting of hydrogen, hydrocarbon alkyl, hydrocarbon aryl, hydrocarbon aralkyl,

furfuryl and tetrahydrofurfuryl, R" is selected from the group of radicals consisting of hydrocarbon alkyl, hydrocarbon aryl, hydrocarbon aralkyl, furfuryl and tetrahydrofurfuryl, and also wherein NR'R is a heterocyclic radical in which R13," is selected from the group of radicals consistin of alkylene and alkyleneoxy-alkylene.

13.-The method of making a relatively more stable and higher melting vulcanization accelerator which comprises reacting a methyl ketone with a sulfenamide vulcanization accelerator having at least one hydrogen atom attached to the amido nitrogen atom thereof.

14. The method which comprises reacting acetone with N-cyclohexyl benzothiazole sulfenamide.

15. The method which comprises reacting acetone with N-isopropyl benzothiazole sulfenamide.

16. The method which comprises reacting acetone with N-cyclohexyl diethylthiocarbamyl sulfenamide.

17. The method of vulcanizing rubber which comprises heating rubber and a relatively small amount of sulfur in the presence of a relatively small amount of reaction product of a ketone and a sulfenamide having at least one hydrogen atom attached to the amido nitrogen atom thereof and selected from the group consisting of thiazoline, thiazole'and thiocarbamyl sulfenamides.

18. A vulcanizable composition comprising rubber, a relatively small amount of sulfur and a relatively small amount of reaction product of a ketone and a sulfenamide having at least one hydrogen atom attached to the amido nitrogen atom thereof and selected from the group consisting of thiazoline, thiazole and thiocarbamyl sulfenamides. 1

19. The vulcanized product resulting from the method of claim 17.

20. A reaction product of methyl ethyl ketone and N-isopropyl benzothiazole sulfenamide.

21. A reaction product of acetophenone and N-isopropyl benzothiazole sulfenamide.

22. The method which comprises reacting methyl ethyl ketone with N-isopropyl benzothiazole sulfenamide.

23. The method which comprises reacting acetophenone with N-isopropyl benzothiazole sulfenamide.

- EDWARD L. CARR.'

REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATES PATENTS 

1. A REACTION PRODUCT OF A KETONE AND A SULFENAMIDE HAVING AT LEAST ONE HYDROGEN ATOM ATTACHED TO THE AMIDO NITROGEN ATOM THEREOF AND SELECTED FROM THE GROUP CONSISTING OF THIAZOLINE, THIAZOLE AND THIOCARBAMYL SULFENAMIDES. 